Side doors on vehicles (e.g., minivans) continue to evolve. One advancement is the use of four-bar linkages to control movement of the side door when the door is moved longitudinally between closed and open positions. Such opening mechanisms potentially result in the side door having a lower stiffness as compared to conventional three-rail side doors. Such lower stiffness is particularly noticeable when the side door is pushed or pulled at the rear-most edge thereof. This potentially creates a negative impact in perceived quality by the customer when pushing or pulling on the side door, which has the potential to give the impression that the door is “cheap” or structurally flimsy, whether this perception is actual or not. Additionally, some market case studies have shown that rigidity of side vehicle doors is important to customers, in particular as concerns leaning against a fully open door and/or waxing the side door when in the open state.